Ni–Mo–B alloys as cathode material for alkaline water electrolysis

The hydrogen evolution reaction (HER) of nanocrystalline Ni–Mo–B alloys was investigated in alkaline solution in comparison with the corresponding crystalline materials and polycrystalline nickel. The nanocrystalline alloys, prepared by melt spinning, were investigated towards the HER in 1 M KOH solution at 298 K. An electrochemical activation procedure (cyclic reduction-oxidation pre-treatment) was used to enhance the apparent HER activity. In case of the crystalline Ni–Mo–B master alloys the origin of the activity can mainly be attributed to an increase of the real surface area (roughening) caused by a dissolution of Mo-containing phases. Interestingly, a roughening of nanocrystalline Ni–Mo–B alloys did not occur, probably, because of the very homogenous and fine microstructure of these materials. The higher HER activity of the nanocrystalline Ni–Mo–B alloys is obviously caused by a higher intrinsic activity of the nanocrystalline Ni–Mo–B alloys and a synergistic effect of Mo. •The HER of nanocrystalline (nc) and polycrystalline Ni–Mo–B alloys was studied.•The origin of the improved activity correlates with the altered microstructure.•The improved HER of polycrystalline alloys originates from Mo phase dissolution.•Activated nc alloys benefit from a higher intrinsic activity (no roughening).